The present invention relates to an ultrasonic joining method and an ultrasonic joining device for connecting paper material, in particular paper, board or paperboard.
WO03/043807 shows a device for connecting a multilayer material web by means of ultrasound. Here, a large-area and continuous connection of individual layers of the material web is made. For instance, corrugated board is produced.
EP 0 340 334 A2 describes a device which is suitable for connecting two-layer or multilayer paper products by means of ultrasound. The paper used here is provided with a thermoplastic coating. By means of the sonotrode, longitudinal waves are generated, so that the sonotrode moves toward the anvil and away from the anvil again during the ultrasonic oscillation. By means of the appropriate ultrasonic frequency and the appropriate contact pressure, adequate compaction of the paper layers is produced here. At the same time, there is a high development of heat in the micro-region of the thermoplastic coating, and thus adhesive bonding of the paper layers occurs.
The appended FIG. 7 shows, in a schematically simplified view, an ultrasonic joining device 100 according to the prior art for connecting thermoplastically coated paper material. The device 100 comprises a sonotrode 102 according to the prior art and an anvil 103 according to the prior art. The paper material 5 to be joined is located between the sonotrode 102 and the anvil 103. In the gap between the sonotrode 102 and the anvil 103, a joining force 106 is applied to the paper material 5. The sonotrode 102 executes an ultrasonic oscillation with an oscillation direction 107. In the device 100 according to the prior art, the oscillation direction 107 and the direction of the joining force 106 are oriented parallel to each other. Here, therefore, the longitudinal direction of movement of the sonotrode 102 is used for the joining process.